// 分段计算水价

# include <stdio.h>

int main(void) {
    double x, y;
    printf("Enter x:");
    scanf("%lf", &x);

    if (x < 0)
        y = 0;
    else if (x <= 15)
        y = 4 * x / 3;
    else
        y = 2.5 * x - 10.5;

    printf("f(%.2f) = %.2f\n", x, y);
    return 0;
}
